This invention relates to a high pressure water control device such as a dump gun for firing high pressure water to break up concrete.
Known dump guns commonly include poppet valves to control the flow of water between a high pressure nozzle and dump. The water can be dumped at low pressure to the surroundings or returned to a water reservoir.
Poppet valves cannot guarantee pressure balance as cone and seat diameters are subject to tolerances and change/wear during use. Also, poppet valves rely on the operator""s hand force to maintain the seal. If this force is relaxed leakage will occur without the operator being aware of any handle movement. This type of leakage leads to very rapid valve/seat erosion failure. Furthermore, poppet valves are very sensitive to erosion failure. This normally results in the seat and cone being scrapped. Erosion failure at high pressures is rapid, unpredictable and almost impossible to avoid.
The invention seeks to overcome or mitigate these drawbacks.
According to one aspect of the present invention, there is provided a high pressure water control device comprising a water inlet, a high pressure water outlet, a low pressure water outlet and a valve for selectively communicating the inlet with one or other of the outlets, wherein the valve is a spool valve.
According to another aspect of the invention there is provided a high pressure water control device in the form of a high pressure water gun comprising a water inlet, a high pressure water outlet, a low pressure water outlet, a spool valve for selectively communicating the inlet with one or other of the outlets, an elongate nozzle terminating in said high pressure outlet and a barrel surrounding the nozzle and terminating in said low pressure outlet.
The invention will now be more particularly described, by way of example, with reference to the accompanying drawings.